Recently I managed to purchase an original Marconi PS213 key, I have in the past make about three loose copies of these now rare and collectable keys with varying levels of success, they have a superb action and are well worth making however without an original to look at it is very difficult to get a very close copy even with a good set of dimensions, I've also seen a few other hand made "Replicas" of this design which although they are lovely keys  are not really even close copies, Anyway seeing as I'm stripping down my original for refurbishment I thought I might have yet another attempt at a serious copy, but this time as I make the various parts I shall fit them into my original to make sure they are as close as I can get them, below you can see I've made a start, the original arm is resting on my copy, I've made this arm a different way by sweating on a couple of cheeks over the arm head and then cutting to shape, this has produced a much closer copy , there are still lots of problems to overcome but that's part of the fun :()
Below you can see a swap of parts, my pivot tightener on the original and an original tightener on my pivot, also a comparison of the two arms and pivots, and my arm and pivot on the original base so far everything is within 1mm which is good for me
 
And now below the key is sitting on its new base with base plate cover, only sharing the original tension adjuster, terminals and knob. and today it became a real key instead of just a collection of parts, this design has a superb action, Marconi got it spot on with this one, I spent an hour selecting the right spring for it and setting it up for a first test, copying a key design to this level is much harder than a look-a-like  everything has to be checked and double checked with quite a few restarts, I had to break my 1mm challenge as the base cover in the original is 5mm thick and I could only obtain 3mm plate to make mine but it's not really a problem as when I finally find some 5mm I shall simply make another plate :()
The connections from the key to the terminals are shown below, the original has large milled slots in which plated brass strips are fitted,  one end connects to the various key parts the other end has a threaded ring, you can see the original strips sitting in the milled slots in the new base, I'm not going to mill out the third terminal slot, as the early versions of this key the AS 300 didn't have a third terminal so I'm told, so a bit of devilment on my part, I shall fit the terminal but not the strip, the third terminal is not really required and will satisfy my urges to "YUH" the key :()
The slot milling was a problem as my Mini Mill was not quite big enough so I had to do the job using a smaller milling tool and a few passes.
but it looks good and very close to the original,
 
Today I spent making the strip connectors that connect the various parts of the key together and noticed a mistake, I had assumed when I made and fitted the contact posts that the fixing bolts would be the same size as the pivot assembly and drilled and tapped accordingly, but in fact they are smaller so when I came to make the terminal strip I realised if I made the strip the same size as the original then it would be impossible to drill a hole to take the now larger bolt which was irritating, I could have filled the post hole drilled and re tapped but that is a real fudge, or bite the bullet and make the contact strip slightly wider, so wider it is as can be seen below, that was quite fiddly work and took a few hours, so I only had time to make one terminal and shaped washer, you can see it below sitting with the two originals on the original base.
Just a gentle plod now that the main construction is nearly over, such as copying the large Marconi knob, below left, and the tension adjuster right
and below that the two ladies side by side for comparison,
 
I will soon have some very difficult decisions to make soon, as to how I finish this key, as you can see it only has the two terminals, like my original, there seems very little information on these keys, there is no doubt that my original is a PS213 but it seems quite an early model as there is no sign of any Nickel plating at all and almost certainly it never had a third terminal as there is a shadow under the two existing terminals where the base is bright and shiny the third is as dull as the rest of the base, unless of course it lost a terminal at a very early age, so do I leave it with just two terminals or fit a third that doesn't do anything, and the finish, my original was once bright and shiny brass and never had the black insulated handle that later keys of this type have, and of course the Nickel plating, I have plated the terminals and washers so I should go ahead and plate the lot but still a bit undecided. Below are the tighteners for the main adjusters, If there is a problem with this design then this is it!! these tighteners are just not man enough for the job, you can see how my original is damaged almost about to break open, I have made quite a few replacements for PS213 owners that have damaged ones, for anyone that has one of these keys buy a few 3mm Pop rivets the metal stem is ideal for adjusting these keys
And below are a few close-ups of the action now the mechanics are almost complete and some pictures to compare the original to my dare I say it "Replica" :()  keeping in mind this is just unfinished machined brass
And finally after lots of thought and discussion I finished the key as my original would have been when it was new, except maybe the third terminal which I met half way by fitting a blank, otherwise it is as perfect as I could make it at the time, the base is about 2mm thinner as is the base cover this is because I couldn't get the correct size material at the time, and a few very minor changes in thread size and material, not the best photos I shall take some better ones later bright shiny brass is difficult to take quality pics. End of project  time taken 12 days, about 60 hrs roughly.  great fun..